dv1394 is disabled by default, do not redundantly disable it on Hurd.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@18946 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

configure

@@ -1698,7 +1698,6 @@ case $target_os in
     gnu/kfreebsd)
         ;;
     gnu)
-        disable dv1394
         ;;
 
     *)